I was having a time trying to visualize this:
"This one's in the name of Samuel C. Laxter," he said, indicating a custom-built sports coupe with spare tires mounted in fender wells on either side. It was a powerful, low-hung car of glistening enamel and chrome steel.
(The Case of the Caretaker's Cat, by Erle Stanley Gardner. Pocket Book edition, 1962, p. 66)

Must have been something along these lines. Pretty cool. Those fender-mounted spare tires don't look nearly as cool on newer cars, though.

Chevrolet discontinued the side-mounted spares in 1936 and Cadillac followed suit in 1940.